The `ggplot2` package incorporates Hadley Wickham's *[Layered Grammar of Graphics](http://vita.had.co.nz/papers/layered-grammar.pdf)* to make beautifully-visualized data for further analysis. This code-through project outlines the basics of making a `ggplot2` visualization, and uses the `mpg` dataset included with the `ggplot2` library. For this example, I examine the relationship between **highway fuel mileage (mpg) and engine displacement (size, in liters)** of vehicles of different types (class).